1. Field of the Invention
The present invention relates to an image communication system capable of visually outputting image data of an image input apparatus and transmitting the image data to a communication line, and a method of controlling the same.
2. Related Background Art
Conventionally, an image photographed by an image input apparatus such as a digital camera is color-printed or sent to a remote partner. FIG. 1 shows the construction of such a prior art image communication system. In FIG. 1, the image communication system comprises a public network 101, a network control unit 102 such as a modem or a terminal adapter, a personal computer (PC) 103, a PC printer 104, a digital camera 105, a communication adapter 106, and a printer 107 dedicated to the digital camera.
FIG. 2 is a block diagram of the construction of the digital camera 105. In FIG. 2, the digital camera 105 comprises a CPU 201, a memory 202, an image input unit 203, an operation unit 204, a PC interface 205, a printer interface 206, a communication adapter interface 207, and a data bus 208.
When an image photographed by the digital camera 105 is to be printed, image data stored in the memory 202 of the digital camera 105 can be received by the personal computer 103 via the PC interface 205 and then output to the PC printer 104 using application software of the personal computer 103.
When image data is to be transmitted, the image data is temporarily received in the personal computer 103, and compressed by application software of the personal computer. The compressed data is transmitted to the network control unit 102, and then to a communication line via the network control unit 102.
By this method, an image photographed by the digital camera can be printed or transmitted via the communication line.
In the absence of the personal computer, the digital camera is directly connected to the dedicated printer 106 or a dedicated modem via the printer interface 206 or the communication adapter interface 207 to print an image or transmit it to the communication line.
In some cases, the digital camera and the printer or the modem are connected to each other via a wireless channel or radio channel.
In this arrangement, the same wireless channel is used to transmit data to the printer and transmit data to the communication line via the modem.
However, when the digital camera is connected to the printer and the modem via a wire, the digital camera must comprise printer and modem interfaces. In addition, if the printer and the modem are not installed near the digital camera, connection between the digital camera and the printer or the modem must be switched.
When the digital camera is connected to the printer or the modem via a wireless channel, if a wireless communication channel having a high transmission rate is used, data can be efficiently transmitted to a printer to which a large amount of data must be sent. However, even when data can be compressed in, e.g., accessing a public network such as ISDN (Integrated Services Digital Network) or PSTN (Public Switched Telephone Network), a wireless communication channel having the same transmission rate as that in transmitting data to the printer is undesirably occupied.
If the digital camera is connected to the printer or the modem using a wireless communication channel having a low transmission rate in consideration of an access to the public network such as ISDN or PSTN, when a large amount of data is needed to be transmitted to the printer, the large amount of data can only be transmitted at a low rate.